Only freeze once the cached JS values of templates

CParamNodes can be quite large, thus we usually cache the JS::Value when
converting them. The AIInterface makes heavy use of it as detected in #7404.

However, the cached values are re-frozen everytime, which is a
significant waste of time on a large number of templates.

source/simulation2/scripting/EngineScriptConversions.cpp

@@ -1,4 +1,4 @@
-/* Copyright (C) 2024 Wildfire Games.
+/* Copyright (C) 2025 Wildfire Games.
  * This file is part of 0 A.D.
  *
  * 0 A.D. is free software: you can redistribute it and/or modify
@@ -69,11 +69,6 @@ template<> void Script::ToJSVal<IComponent*>(const ScriptRequest& rq,  JS::Mutab
 template<> void Script::ToJSVal<CParamNode>(const ScriptRequest& rq,  JS::MutableHandleValue ret, CParamNode const& val)
 {
 	val.ToJSVal(rq, true, ret);
-
-	// Prevent modifications to the object, so that it's safe to share between
-	// components and to reconstruct on deserialization
-	if (ret.isObject())
-		Script::DeepFreezeObject(rq, ret);
 }
 
 template<> void Script::ToJSVal<const CParamNode*>(const ScriptRequest& rq,  JS::MutableHandleValue ret, const CParamNode* const& val)

source/simulation2/system/ParamNode.cpp

@@ -1,4 +1,4 @@
-/* Copyright (C) 2024 Wildfire Games.
+/* Copyright (C) 2025 Wildfire Games.
  * This file is part of 0 A.D.
  *
  * 0 A.D. is free software: you can redistribute it and/or modify
@@ -25,6 +25,7 @@
 #include "ps/CStrIntern.h"
 #include "ps/Filesystem.h"
 #include "ps/XML/Xeromyces.h"
+#include "scriptinterface/Object.h"
 #include "scriptinterface/ScriptRequest.h"
 
 #include <boost/algorithm/string/classification.hpp>
@@ -382,7 +383,12 @@ void CParamNode::ToJSVal(const ScriptRequest& rq, bool cacheValue, JS::MutableHa
 	ConstructJSVal(rq, ret);
 
 	if (cacheValue)
+	{
+		if (ret.isObject())
+			Script::DeepFreezeObject(rq, ret);
+
 		m_ScriptVal.reset(new JS::PersistentRootedValue(rq.cx, ret));
+	}
 }
 
 void CParamNode::ConstructJSVal(const ScriptRequest& rq, JS::MutableHandleValue ret) const

source/simulation2/system/ParamNode.h

@@ -1,4 +1,4 @@
-/* Copyright (C) 2022 Wildfire Games.
+/* Copyright (C) 2025 Wildfire Games.
  * This file is part of 0 A.D.
  *
  * 0 A.D. is free software: you can redistribute it and/or modify
@@ -252,6 +252,8 @@ public:
 	 * If @p cacheValue is true, then the same JS::Value will be returned each time
 	 * this is called (regardless of whether you passed the same @p cx - be careful
 	 * to only use the cache in one context).
+	 * Cached object values are frozen, using DeepFreezeObject, so that it's safe to
+	 * share between components and to reconstruct on deserialization.
 	 * When caching, the lifetime of @p cx must be longer than the lifetime of this node.
 	 * The cache will be reset if *this* node is modified (e.g. by LoadXML),
 	 * but *not* if any child nodes are modified (so don't do that).